The growth of AlN crystals on c-plane 6H-SiC substrates by thermal nitridation of Al2O3 pellets in the presence of graphite and ZrO2 was demonstrated. Addition of graphite and ZrO2 effectively accelerated the evaporation of Al2O3, yielding c-axis oriented AlN films on SiC substrates. The SiC substrate was severely deteriorated at 2173K, which produced a porous interface between the AlN film and substrate, resulting in low-quality AlN crystals. The deterioration of SiC was successfully suppressed by introducing a pre-deposited homo-buffer layer, allowing two-dimensional-like growth of AlN. The buffer layer promoted the formation of a high-quality AlN film. At 2173K, the full-width at half maximum of the X-ray rocking curves of the (0002) and (10-10) planes of the AlN film was 360 and 425arcsec, respectively.